From: shaozhengchao <shaozhengchao@huawei.com>
To: <sdf@google.com>, Lorenz Bauer <oss@lmb.io>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>, <bpf@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <yuehaibing@huawei.com>
Subject: Re: [PATCH v4,bpf-next] bpf: Don't redirect packets with invalid pkt_len
Date: Sat, 15 Oct 2022 10:36:46 +0800 [thread overview]
Message-ID: <ce5d58a3-32ed-fa81-d490-ce854cfca927@huawei.com> (raw)
In-Reply-To: <Y0mUjLXEpVuheSUc@google.com>
On 2022/10/15 0:55, sdf@google.com wrote:
> On 10/14, Lorenz Bauer wrote:
>> On Thu, 13 Oct 2022, at 11:44, shaozhengchao wrote:
>> > Sorry, I haven't fully understood your intentions yet.
>> > Can you explain it more detail?
>
>> I'll try! Roughly, we do the following:
>
>> 1. Create a BPF_PROG_TYPE_SOCKET_FILTER program that just returns 0
>> 2. Load the program into the kernel
>> 3. Call BPF_PROG_RUN with data_size_in == 14
>
>> After your bugfix, it seems like step 3 is rejected due to
>> data_size_in == 14. We had to increase data_size_in to 15 to
>> avoid this, see [0].
>
>> This breaks user space, so it would be great if you could fix this in
>> a way that doesn't refuse BPF_PROG_RUN with
>
> [..]
>
>> data_size_in == 14. Since I don't understand the original problem very
>> well I can't tell you what the best fix is however.
>
> The problem was that we were able to generate skb with len=0 via
> BPF_PROG_RUN. Prohibiting those cases breaks backwards compatibility, so
> we either have to:
>
> a) (preferred?) accept inputs with <14, but maybe internally pad to 14
> bytes to make the core stack happy
> b) revert the patch and instead have length checks at runtime; doesn't
> seem to
> be worth the penalty in the forwarding path because of some corner cases
> like these ?
>
Hi sdf:
a) looks better and I'll put up a patch as soon as possible to
fix it.
Zhengchao Shao
>
>> 0:
>> https://github.com/cilium/ebpf/commit/a38fb6b5a46ab3b5639ea4d421232a10013596c0
>
>> Thanks
>> Lorenz
next prev parent reply other threads:[~2022-10-15 2:36 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-15 11:55 [PATCH v4,bpf-next] bpf: Don't redirect packets with invalid pkt_len Zhengchao Shao
2022-07-15 23:30 ` Stanislav Fomichev
2022-07-19 17:00 ` patchwork-bot+netdevbpf
2022-09-14 11:19 ` Lorenz Bauer
2022-09-17 15:46 ` Stanislav Fomichev
2022-09-19 10:55 ` shaozhengchao
2022-09-20 14:42 ` Lorenz Bauer
2022-09-21 8:48 ` shaozhengchao
2022-09-21 20:59 ` Stanislav Fomichev
2022-10-13 9:36 ` Lorenz Bauer
2022-10-13 10:44 ` shaozhengchao
2022-10-14 16:29 ` Lorenz Bauer
2022-10-14 16:55 ` sdf
2022-10-15 2:36 ` shaozhengchao [this message]
2022-11-03 21:07 ` Martin KaFai Lau
2022-11-03 21:36 ` Stanislav Fomichev
2022-11-03 22:42 ` Martin KaFai Lau
2022-11-03 22:58 ` Stanislav Fomichev
2022-11-09 21:43 ` Stanislav Fomichev
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